BOLIVAR PENINSULA, Texas -

Investigators have released a crucial clue in the case of two women found dead Friday on the Bolivar Peninsula.

The bodies of Britney Cosby and Crystal Jackson, both 24, were discovered Friday morning behind a Bolivar convenience store. Both victims were from southeast Houston.

Investigators with the Galveston County Sheriff's Office believe the suspect may have killed the women somewhere else and then placed their bodies near a dumpster.

The sheriff's office has released a sketch of a suspect they say was last seen with the two women and their vehicle.

Authorities say the women died "horrible and terrible" deaths.

An autopsy was performed Saturday on Crosby. The medical examiner determined her cause of death to be blunt force trauma.

Officials say Jackson was shot to death.

The sheriff's office believes both women were killed about eight hours before they were left at the dumpster.

Brittney Cosby's great grandmother, Annie Lee Cosby, last saw her early Thursday morning before Brittney left for work. Annile Lee Cosby raised her from the age of two. As an adult, Britney had cared for her great grandmother after she became ill and lost one of her legs.

"Everything to be done, she did it. So she was a good child and I don't know not what I'm going to do without her," said Annie Lee.

Deputies are asking anyone with information to come forward.

They would like to hear from anyone who knows where the women may have last been seen, or who may have spoken to them last.

Authorities are also looking for Cosby's 2006 silver Kia Sorento, which is now considered stolen. The vehicle had paper license plates.

If you have information in this case, you're asked to call the Galveston County Sheriff's Office at 866-248-8477 or Galveston County Crime Stoppers 409-763-8477.